This invention relates in general to brake drums and, in particular, to an improved method for final balancing a brake drum provided with an integral squealer band.
The production of cast metal brake drums for heavy duty vehicles begins with a conventional sand-patterned mold casting operation. After cleaning, the brake drum casting is precision drilled and concentrically machined to predetermined dimensional tolerances. However, at this point, the machined brake drum typically incorporates a sufficient imbalance which renders the brake drum unsatisfactory for use on a vehicle. As a result of this, the brake drum is generally subjected to a "final balancing" operation. Conventionally, this final balancing operation has been achieved by determining the location and amount of the imbalance using a static balancer, and then welding correcting weights to an outer surface of the drum.
Typically, a heavy duty brake drum is provided with an integral raised squealer band. One method which can be used to final balance a brake drum having a squealer band subjects the drum to a final machining operation. According to this method, a static balancer is first used to determine the location and amount of the imbalance. An operator then marks the location of the imbalance on the squealer band, and transfers the marked drum to a milling machine. The milling machine is operated and flattens off an outer surface of the squealer band at the marked imbalance location to produce a final balanced brake drum.
U.S. Pat. No. 4,986,149 to Carmel et al. discloses another method for correcting the imbalance in a brake drum having an integral squealer band by subjecting the drum to a final machining operation. According to the method of this patent, a static balancer is first used to determine the location and amount of the imbalance. Then, a crescent or wedge of material is preferably cut away from an outer surface of a squealer band of the brake drum by a lathe during an eccentric turning process to produce a final balanced brake drum.